Fig. 2

Dark vs typical microglia’s interactions with dystrophic neurites and Aβ plaques. Representative 5 nm resolution scanning electron microscopy images captured in the ventral hippocampus CA1 stratum lacunosum-moleculare of 20-month-old APP-PS1 male mice. A Typical microglia (TM) observed near extracellular fibrillar Aβ (pseudocolored in purple) and dystrophic neurites (pseudocolored in pink). B Dark microglia (DM) interacting with several dystrophic neurites along with fibrillar Aβ. C–F Quantitative graphs representing the numbers of contacts with dystrophic neurites (C) and Aβ plaques (D) as well as the proportion of microglial cells contacting dystrophic neurites (E) or Aβ plaques (F). Data are shown as individual dots of either 0 or 100 values and are expressed as means ± S.E.M. * p < 0.05, ** p < 0.01, using a non-parametric Mann–Whitney test. Statistical tests were performed on n = 9–12 microglia per animal with N = 3 mice/group, for a total of 111 microglial cell bodies analyzed. Purple pseudo-coloring = fibrillar Aβ, pink pseudo-coloring = dystrophic neurites, red outline = plasma membrane, yellow outline = nuclear membrane, orange asterisk = mitochondria, green asterisk = altered mitochondria, blue asterisk = endoplasmic reticulum, purple asterisk = dilated endoplasmic reticulum, red arrow = Golgi apparatus, 2nd = secondary lysosome, A = axon terminal